I could never play without a great deal of CC, because I both downloaded stuff for my royals and high nobility (stuff that don't exist at all in vanilla game like tiaras and sashes), and I created many cc painted portraits (larger than what can be done on the easel) to tell their story over several generations. I could probably get rid of 90% of the cc clothing and bb but I'd need to keep quite a lot.
Talking about mods is a different story. There are only 3 mods that I really need ; the UI Extension, the let go of white outlines when pointing on sims/objects, and the no-blur (I'm grown up enough to watch pixel skin and there's not much to see anyway, but the setting of a situation (say in a bat tub or breastfeeding) get's totally ruined when the sim is covered in pixels.) Only UI Extension breaks when game is patched, but the creator has always fixed it impressively quickly. I have a few more mods that I'm not sure are still working, so I could definitely do a Spring cleaning...
If I was to start a brand new save, I think it could b fun playing vanilla, though (including those 3 mods). When game was new there was a lack of alternatives in CAS and BB, but with most packs added, I'm pretty sure the game offers more than I would need anyway.